In certain known types of compression-type gas machines, such as air compressors, an elastic bellows or diaphragm bounding one side of a working chamber is alternately operated by means of a reciprocating piston or other actuating means between an expanded and a compressed position, thereby defining a working cycle of the compressor.
Machines of this type depend for their efficiency on the maintenance of good contact between the actuator and the diaphragm surface. One problem in present designs is that during the suction stroke, residual atmospheric pressure operating on the diaphragm on the external side of the working chamber tends to partially collapse the diaphragm, particularly when its stiffness is low. As a result, the diaphragm tends to move out of contact with the actuator as the latter retracts. The resulting reduction in volume within the working chamber tends to reduce the volume of gas sucked into the working chamber during the suction stroke, so that the efficiency of such arrangements are relatively low.